1. Field of the Invention
The present invention relates to a communication system, a communication apparatus which can be connected to a communication system, a control method for a communication system, and a control method for a communication apparatus which can be connected to a communication system.
2. Description of the Related Art
In recent years, in order to attain higher-speed terminal devices and a higher-speed network that connects terminals, a network system which uses a network built by a multi-channel transmission path using a plurality of channels has been examined.
As shown in FIG. 9, a node device and network system of this type comprise a node device 911 for connecting a plurality of terminal devices 971 and 978, and a multi-channel transmission path 900 which connects a plurality of such node devices, and uses a plurality of channels. In the network system shown in FIG. 9, a packet which is transmitted from the terminal device 971 and input to an input I/F unit 941 is switched by a switch fabric 921 so as to be transmitted onto the multi-channel transmission path from one of a plurality of transmitters 951 to 958, and is output to a predetermined transmitter. Then, the packet is output onto the multi-channel transmission path. After that, the packet is relayed by node devices inserted before the node device connected with a destination terminal device, and is finally received by the receiver of the target node device. Furthermore, the destination of the packet is controlled by a switch fabric, so that the packet is output from an output I/F unit connected with the destination receiving terminal, and the packet is then received by the terminal device. The switch fabric 921 of the node device serves to route a packet to a desired terminal device of a desired node device by controlling switching, i.e., determining one of a plurality of transmitters or output I/F units to which the input packet is to be output.
The switch fabric used in the prior art normally comprises a cross-bar type switch having N inputs and N outputs. The number N of inputs is the sum of the numbers of receivers and input I/F units, and similarly, the number N of outputs is the sum of the numbers of transmitters and output I/F units.
A packet switched by the switch fabric is normally made up of address information indicating the destination terminal of that packet, and data information carried by the packet. The switch fabric has a function of temporarily storing the destination address of the input packet, compares the stored address with those of all the terminal devices connected to the network system, which are written in a memory table, and switches to output the packet to a desired output terminal. In this case, since occurrence of output congestion pertaining to inputs must be detected to execute arbitration control so that a packet input to an input terminal is output from a predetermined output terminal, the hardware scale of this controller increases.
Japanese Patent Laid-Open Nos. 5-260060 and 4-176232 disclose other network configurations which transmit signals using a plurality of channels.
Japanese Patent Laid-Open No. 5-260060 discloses a technique that finds an empty one of a plurality of rings by search, and transmits in turn signals segmented at equal intervals onto the empty ring.
Japanese Patent Laid-Open No. 4-176232 discloses a technique for transmitting packets by distributing them in a predetermined order. FIG. 9 of Japanese Patent Laid-Open No. 4-176232 in question discloses a technique that outputs signals sent via a plurality of channels onto a plurality of sub transmission paths using an ATM switch. The ATM switch outputs signals sent via m channels to n reception buffers as m systems of signals, and the reception buffers read out the m systems of input signals in a predetermined order.
Furthermore, Japanese Patent Laid-Open Nos. 8-172394 and 8-237306 disclose a network system that changes channels of a main transmission path.
It is an object of the present invention to efficiently output signals sent via a plurality of channels onto a plurality of sub transmission paths.
It is another object of the present invention to output signals sent on a plurality of channels toward sub transmission paths by selecting necessary signals.
It is still another object of the present invention to efficiently input signals sent via a plurality of sub transmission paths to a plurality of channels.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.